Method and apparatus for controlling the contour of rolls in a rolling mill



2,903,926 LLING THE 0 MILL.

Sept. 15, 1959 I R. M. REICHL METHOD AND APPARATUS FOR CONTRO CONTOUR OF ROLLS IN A ROLLIN 3 Sheets-Sheet 1 Filed Jan. 11, 1956 T v //I///////////// INVENTOR. REYMolvo 0!, REM HL ATTORN S Sept. 15, 1959 R. M. REICHL 2,903,926

METHOD AND APPARATUS FOR GONTROLLING THE CONTOUR 0F ROLLS IN A ROLLING MILL Filed Jan. 11, 1956 I, 3 Sheets-Sheet 2 I N V EN TOR. RYMO-0 lW, RE/CHL- R. M. REICHL METHOD AND APPARATUS FOR CONTROLLING THE Se t. 15, 1959 CONTOUR OF ROLLS IN A ROLLING MILL 3 Sheets-Sheef 3 Filed Jan. 11, 1956 nited States Patent Patented Sept. 15, 1959 liice METHOD AND APPARATUS FOR CONTROLLING TIE CONTOUR OF ROLLS IN A ROLLING MILL Reymond M. Reichl, Forest Hills, N.Y., assignor to Baldwin-Lima-Hamilton Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application January 11, 1956, Serial No. 558,516

Claims. (Cl. 80-56) This invention relates to a method and to apparatus for controlling the contour of the working rolls of a rolling mill to compensate for changes in the conditions under which they are working.

During both hot and cold rolling, the Working rolls tend to expand due to increases in their temperature and to deflect with the roll pressure. The resulting change in the contour of the roll is normally the greatest near its mid-point. In order to compensate for these changes, the working faces of the rolls are ground to a predetermined contour which is non-cylindrical and usually convex.

In the rolling of sheets of uniform thickness, the rolls are normally set at a given spacing and to exert a given pressure on the slab, ingot or other stock being rolled to eflect reduction to the desired thickness. If, however, a slab or ingot of greater or lesser thickness enters be tween the rolls, or it hard or soft spots are encountered in a slab or ingot, or, in hot rolling, if the temperature of the slab or ingot or a portion thereof varies materially from the desired temperature, the rolls will move closer together or farther apart as less or greater resistance is encountered, and variations in the sheet will inevitably result.

It is known that such variations in the thickness of a sheet can be avoided within certain limits by changing the pressure applied by the working rolls of the mill to compensate for the changes in the resistance of the metal being rolled. Methods and apparatus have heretofore been developed by which the roll pressure is automatically adjusted to compensate for variations in the resistance of the metal being rolled. One such method and apparatus is described in the co-pending application Serial No. 444,- 106, filed July 19, 1954, by Reymond M. Reichl and George N. Landis. However, the changing pressure ap plied by the rolls, or conversely, the changing separation resistance of the metal between the rolls, causes a chang ing deflection of the rolls, which itself may introduce nonuniformity in the thickness of the sheet.

In the rolling of tapered metal sheets the difliculties arising from the deflection of the working rolls are even greater than in rolling sheets of uniform thickness. In such taper rolling, the pressure under which the rolls work is continuously changing during each pass. The separating pressure between the rolls may, for example, have a certain value at the beginning of a pass and increase two or three fold during the pass. This changing separation pressure causes a continuous change in the deflection of the rolls, the extent of which depends upon the degree of taper being imparted to the sheet. The continuous change in the deflection of the rolls, in turn, causes waves and non-uniformity in the rolled sheet which cannot be removed by stretching, leveling or the like.

It is known that roll contour can be corrected, for example, in a four high rolling mill which has convexly ground work rolls by positioning a hydraulic cylinder between the chocks of the upper and lower work rolls. The hydraulic cylinders may, for example, be located in the chocks of the lower work-roll, with their rams bearing against the chocks of the upper work-roll. This arrangement permits an operator to alter the contour of the work rolls by changing the hydraulic pressure a plied to the rams.

The use of hydraulic cylinders in this manner does not prevent non-uniformity in the thickness of a rolled sheet arising from deflections in the working rolls, since the operator can compensate for the changes in the contour of the rolls only after defects in the sheet have appeared. This is particularly true in the rapid rolling of tapered sheets in which very strong increases or decreases in the pressure on the rolls occur in a single pass. It has not been possible according to prior art practice to apply suitable correction for the deflection of the working rolls particularly in taper rolling operations and this deflection has led to unsatisfactory products, particularly in the case of tapered sheets.

It is an object of this invention to provide means for continuously correcting the contour of the working rolls of a rolling mill in accordance with changes in roll pressure during the rolling operation.

Another object of this invention is to provide means for continuously adjusting the contour of the working rolls of a rolling mill in accordance with the increases or decreases in the pressure on the rolls which take place during a taper rolling operation.

A further object is to provide means for continuously and automatically adjusting and correcting the contour of the working rolls of a rolling mill in accordance with changes in roll pressure in synchrony with said changes in pressure with no perceptible time-lag between the changes in the roll pressure and the synchronized correction.

Various other objects and advantages of the invention will appear in the detailed description of a preferred embodiment of my invention which follows.

In the practice of my invention, a slab, ingot or sheet or other work-piece is passed between two opposed working rolls of a rolling mill which carries at least one backup roll for each of the working rolls, while exerting a pressure between the adjacent chocks of the working rolls which is in a direct ratio to the pressure exerted by the working rolls on the sheet passing between them. The pressure exerted between the adjacent chocks of the working rolls may be applied by hydraulic rams, positioned between each pair of adjacent chocks, each of which has The pressure exerted by the working rolls on the sheet passing between them may be conveniently measured in terms of the strain placed upon the stand or housing of the rolling mill which carries the chocks of the rolls, for example, by a strain gauge aflixed to the mill housing.

The control system in accordance with my invention, comprises essentially a means for measuring the strain placed upon the housing of a rolling mill having two working rolls and at least two backing rolls, hydraulic rams positioned between the adjacent chocks of the upper and lower working rolls, a hydraulic system for supplying a liquid under pressure to the cylinders of the said rams, and a control system which regulates the pressure at which the liquid is supplied to the hydraulic rams to maintain such pressure at all times at a level which 7 is in direct proportion to the strain or stretch on the housing of the rolling mill. The strain on the housing or roll stand is created by the pressure exerted by the working rolls on the sheet being rolled so that a strain gauge, in effect, measures the pressure exerted by those rolls. In place of the usual strain gauge and electrical control system the separation between the upper and 5. sure valve 21 and hence controls the pressure of the oil to the cylinders 18, 18 in a manner hereafter described.

The pressure on the hydraulic fluid in conduit 20 and in the hydraulic cylinders 18, 18, 18, 18 is determined by the extent to which the pump pressure is relieved by the action of the main pressure relief valve 21, controlled by the pilot valve 59, in by-passing hydraulic fluid through the conduit 25 back to the reservoir 26. An excess of the fluid is normally supplied to the main relief valve 21 and a portion of the hydraulicfluid supplied to the main relief valve 21 is continually by-passed to the reservoir 26. The setting of the main relief valve 21 is automatically controlled through the strain gauge 30 and pilot valve 59, by the pressure under which the rolls 13 and 14 are working, and this, in turn, controls the quantity of the hydraulic fluid by-passed to the reservoir 26 and automatically controls the pressure applied by the hydraulic jacks 17, 17 between each of the adjacent pairs of roll chocks 15, 15 and 16, 16.

When the working rolls 13 and 14 and the back-up rolls 11 and 12 deflect under the resistance of the metal being rolled, hydraulic pressure on the pistons 19, 19 causing the ohocks to separate, will deflect the ends of the rolls 13 and 14 to compensate for the working deflections in the opposite direction. By a suitable adjustment of the hydraulic pressure by the action of the main relief valve 21, a deflection of the rolls is obtained which exactly compensates for this Working deflection and a uniform gap between the working rolls 13 and 14 is thereby maintained, even in the case of a substantial variation in the rolling pressure.

This hydraulic deflection of the working rolls 13 and 14 to compensate for their working deflection is caused to take place automatically by the action of the resistance strain gauge 30 mounted on one of the rolling mill housings in such a position as to register increases or decreases of strain on the housing produced by increases or decreases in the pressure under which the rolls 13 and 14 are working during the rolling operation. Strain gauges of this type are described, for example, in the book entitled Resistance Strain Gauges, by I. Yarnel, published August 1951, by Electronic Engineering, 28 Essex Street, Strand, London W.C. 2, England, or in United States Patent No. 2,292,549, granted August 11, 1952, however, other electrical or mechanical strain measuring devices may be used.

When the pressure on the working rolls 13 and 14 is increased or decreased, this change in pressure is transmitted to the back-up rolls 11 and 12, or to a back-up roll train and through the screwdown mechanisms 10a to the mill housings 10. The mill housings 10 will hence re ister the degree of increase or decrease in pressure on the working rolls, as strain on the housings which is reflected in the strain gauge 30 mounted on the housing 10.

The electrical resistance of the strain gauge 36 increases or decreases with increases or decreases in the strain on the mill housing during a taper or other rolling operation. This changing electrical resistance in the strain gauge 30 is used to control the changes in setting of the main pressure relief valve 21 through the pilot relief valve 59 by means of a servo system consisting of a synchro electrical control system and a hydraulic control system. Synchro electrical control systems of the general type which I utilize are described in the Electronic Control Handbook by Ralph R. Batcher and William Moulic, published in 1946 by Caldwell-Clements, Inc., 480 Lexington Avenue, New York 17, N.Y., on pages 233 to 237, inclusive, and can be purchased from manufacturers of this type of equipment.

Referring specifically to Figures 7 and 9, which illustrate diagrammatically an electrical and hydraulic control system suitable for the practice of my invention, the strain gauge 30 is connected with the electrical conductors 31 and 32 through which an electrical current of low amperage flows from the amplifier 33. The changes in the resistance of the strain gauge 30, created by changes in the working pressure of rolls 13 and 14, change the voltage of the current flowing through it. The strain gauge current is electronically amplified by the amplifier 33 and the higher voltage output of the amplifier is fed through electrical connections 34 and 35 to a torque motor 36 which is balanced against a spring 37. One of the electrical connections 34 or 35, illustrated as conductor 35, passes through a rheostat 38 by which the voltage of the electric current supplied by the amplifier 33 to'the torque motor 36 can be readily adjusted. The angular deviation of the torque motor 36, produced by the varying voltage of its current supply, is directly proportional to the strain on the mill housing 10, as measured by changes in the resistance of the strain gauge 30.

The rotor of synchro generator 40 of an electrical synchro system is mechanically connected to the torque motor 36 by a shaft 41. There is no electrical connection between the torque motor 36 and the synchro control combination which I utilize. The control transmitted by the torque motor 36 to the synchro system is solely in terms of the mechanical angular deviation of the shaft 41.

The stator of the synchro generator 40 is electrically connected to the stator of a synchro motor or rotatable position control transformer 42 by three electrical connections 43, 43, 43 as more clearly shown by Figure 9. The rotor of the position control transformer 42 is mechanically linked to the rotor of drive motor 50 by the shaft 51, and is electrically connected by conductors 48, 48 to an amplifier and motor control assembly 49 to control the power required to operate the drive motor 50. Power for the motor control assembly 49 and motor 50 is fed through a three wire electrical circuit 53. The drive motor 50 is, in turn, mechanically connected through the reducing gears 56 and 57, and shaft 58 to the pilot relief valve 59 to adjust a spring in the pilot relief valve 59 and thus control the degree of opening or closing of the valve 59 which, in turn, controls the amount of pressure applied to the cylinders 18, 18 through the main pressure relief valve 21. The rotor of the synchro generator 40 is connected to an alternating cur rent source by the electrical connections 60, v60 (Fig. 9).

The synchro generator 40 receives information as to the angular deviation of the torque motor 36 through the shaft 41. This mechanical shaft angle information is converted into a combination of voltages which are transmitted through the electrical connections 43, 43 and 43 to the stator of position control transformer 42. The rotor of the position control transformer or synchro motor 42 produces an electrical voltage in lines 48 when its shaft is not in angular positional agreement with that of the rotor of the synchro generator 40. The current or so-called error signal produced by the rotor of the position control transformer 42, is introduced into the amplifier and motor control assembly 49 to cause rotation of the rotor of the drive motor 50 which, in turn, adjusts the pilot relief valve 59 to cause the pressure of the hydraulic fluid from the main relief valve 21 to increase or decrease in the pipe 20. The direction in which the shaft of the drive motor 50 turns and the extent of its rotation is determined by the direction and extent to which the rotor of the position control transformer 42 is not in angular positional agreement with the rotor of generator 40.

When the rotor of the synchro motor 42 is at exactly the same position as the rotor of the synchro generator 40, no current is generated in the stators of the motor and the generator, and hence, no current is supplied to the drive motor 50 by the stator of the position control transformer 42. On the other hand, such current is supplied as long as the rotor of the synchro motor 42 is not in the same angular position as the angular position of the rotor ofthe synchro generator 40;

As the motor 50 drives the gear train 56, 57 to adjust the pilot relief valve 59*, it also moves the rotor of position control transformer 42 to which it is connected by shaft 51 to bring the rotor of transformer 42 into synchronous position with the rotor of generator 40 when the propercorrection has been made, at which position no further current flows in transformer 42 and rotation of the motor 50 ceases. While these operations have been described in terms of a single change in the position of the pilot relief valve 59 to correspond to a change in strain on the mill housing, it will be understood that in a rolling operation the pressures on the mill stand are constantly changing and that the position of the pilot relief valve 59 is constantly being adjusted to change the pressure in the hydraulic cylinders 18, 18, 18, 18 to correct the working roll contours and that my invention provides in effect a constant floating correction of the pressure relief valve 59 to automatically and simultaneously change the working roll contour in accordance with changes of pressure in the rolling operation.

In this electrical control of the pilot relief valve 59, it will be noted that the strain gauge 30 controls the angular deviation of the torque motor 36, which, in turn, controls the angular position of the rotor of the synchro generator 40. On the other hand, the angular position of the rotor of the synchro motor 42 is restored by the mechanical linkage 51 between the drive motor 58 and the rotor of the control transformer 42. When at any time the angular deviation of the torque motor 36 changes the position of the rotor of the synchro generator 40, with respect to the position of the rotor of the synchro motor 42, the stators of the synchro generator 40 and synchro motor 42 provide current to furnish power to rotate the motor 50 to adjust the pilot relief valve 59, as required by the angular deviation of the torque motor 36 and at the same time to bring the rotors of the synchro system back into registry when the required correction has been made. By means of this system the strain gauge 30 produces a continual adjustment of the pilot relief valve 59, without over-adjustment.

The pilot relief valve 59 is connected by a conduit 62 to the main relief valve 21 and to the reservoir 26 by the conduit 63 for hydraulic fluid. The pilot relief valve 59 adjusts the setting of the main relief valve 21 by permitting hydraulic fluid to flow from the main relief valve 21 through conduit 62, through the pilot valve 59, itself, and finally through conduit 63 to the reservoir 26. As the position of the main relief valve 21 is changed it by-passes more or less oil through the conduit 25 back to the reservoir 26. By this means, the pilot relief valve 59 continually adjusts the setting of the main relief valve 21 in terms of its own setting and continuously adjusts the pressure in the line 20 leading to the cylinders 18, 18.

As an alternative to the use of the combination of a pilot relief valve 59 and a main relief valve 21, illustrated by Figure 7, I may utilize a single valve which performs the functions of both. While various forms of main relief valve 21 and pilot relief valve 59 may be used to control the pressure on the hydraulic fluid in the cylinders 18, 18, 18, 18, a combination valve which I have found particularly suitable for this purpose is illustrated by Figures 10, 11 and 12 This valve provides a combination of main relief valve and pilot valve in one casing and may be used for the main relief valve 21 and the pilot relief valve '9 upon connection to the spring adjustment shaft 58 driven from the motor 50. The use of this valve eliminates the necessity for the conduits 62 and 63 for hydraulic fluid to and from the pilot relief valve 59 as shown in Figure 7, as well as for a separate pilot relief valve 59. In describing this valve with specific reference to Figures 10, 11 and 12, I shall indicate its connections in this alternative embodiment of my invention, with the parts already described with reference to Figure 7.

Referring specifically to Figures 10, 11 and 12, this valve consists of a body 70 to which a cover section 71 is attached, as for example, by stud bolts, with a sealing gasket 72 interposed between the two parts. The body 70 is provided with an inlet port 73 to which conduit 22 (Figure 7) is attached as by a threaded joint, an outlet port 74 to which conduit 20 (Figure 7) is attached and a by-pass port 75 to which conduit 25 (Figure 7) is attached.

The body 70 carries a piston 76 which is loaded by a spring 77 and at one end seats against a valve-seat 78. The piston 76 is cylindrical and is fitted within the valve body 70 with a substantially liquid-tight sliding fit, but has an orifice 79 extending through its body. The lower portion 76a of the piston 76 is slender so that it does not block the direct passage of a hydraulic fluid from the inlet port 73 to the outlet port 74. The end 80 of piston 76 is shaped to form a liquid-tight joint when forced into contact with the valve seat 78.

The upper portion 82 of the piston 76 is equal in diameter to the lower portion 76a and is fitted into a cylindrical opening in the cover 71, while leaving a chamber 83 between its main body section and the cover 71. The orifice 84 connects the chamber 83 with a chamber 85. The orifice 84 is larger in diameter than the orifice 79. This difference between these orifices is essential to the functioning of this valve as will be explained hereinafter.

A pressure control ball valve 86 fitted in a closely fitting seat 87 and held in position by an adjustable spring 88, closes the end of the chamber and its connection with chamber 89. The chamber 89 is connected by orifice 98, extending through the piston 76, to the by-pass port 75 of the valve.

The end of the adjustable spring 88, opposite that which bears on the pressure control ball valve 86, bears on the end of the adjustment screw 91 which is threaded in a packing retainer 92. This retainer also holds in position a gasket 93 and packing 94 which makes this connection liquid-tight. The screw 91 is afiixed to the end of the spring adjustment shaft 58 to permit its rotation by the drive motor 50 to move the screw 91 in and out and vary the pressure on the spring 38.

The functioning of this valve can best be understood by a comparison of Figures 10 and 12, which show the valve in its closed and open positions, respectively. The control of its operation as a pressure control mechanism is the tension or load which is placed on the spring 88 by the adjustment of the screw Q1, the position of which is controlled by the shaft 58. The force with which the ball 86 is held against or near its seat 87 to keep the end of the chamber 85 closed or partially closed is controlled by the rotation of shaft 58.

Referring specifically to Figure 10, it will be noted that when the valve is in closed position, that hydraulic fluid entering through port 73 flows around the lower portion 76a of piston 76 and out through the port 74 and conduit 20 with none of the fluid passing out through the by-pass port 75. In this position the full hydraulic pressure in the line 22 will be transmitted to the cylinders 18, 18. A portion of the hydraulic fluid will pass through orifice 79 into chamber 83 and through orifice 84 and into chamber 85. The fluid cannot escape from chamber 85 into chamber 89 since the port between these chambers is sealed by the ball 86 which is held in position by the tension or load on the adjustment spring 88. In this condition the fluid pressures on the top surface 76b and the bottom surface 760 of piston 76 will be equal and the end 80 of the piston will remain on its seat 78.

When the pressure of the hydraulic fluid in chamber 85 becomes sufliciently high to overcome the resistance of the adjustment spring 88, or conversely, when the resistance of the spring 88 is reduced by an adjustment of the screw 91, the hydraulic fluid escapes from chamber 85 around the pressure control ball 86. This escaping hydraulic fluid flows through chamber 89, orifice 90 in the piston and out through the by-pass port 75.

As the hydraulic fluid tends to flow in through the relatively small orifice '79 at a lesser rate than it tends to flow out of the larger passage 84, the pressure of the fluid in chamber 83 is reduced more than the pressure on the bottom surface 760 of the valve piston 76. The reduction of the pressure in chamber 83 permits the piston 76 to rise against the pressure of spring '77 to displace the piston from its seat 78, as illustrated by Figure 12, and permit a portion of the hydraulic fluid to flow directly from the inlet port 73 to the bypass port 75. This by-passing of a portion of the fluid reduces the pressure on the fluid at the outlet port 74 and, hence reduces the pressure in the cylinders 18, 18 and permits the Working roll chocks and 16 to move closer together.

When the pressure on the fluid has been reduced to an extent substantially corresponding to the respective adjustment of spring 88, the latter will cause ball 86 to contact or approach its seat 87. The pressures on the fluid above and below piston 76 will now be equalized to a greater or lesser degree and spring 77 will cause piston '76 to move downwardly to close or partially close the passage to by-pass port 75.

In the reverse operation of the main pressure relief valve, if the resistance of spring 88 is increased by an adjustment of screw 91, the pump 23 which as mentioned hereinbefore supplies an excess of fluid to the main pressure relief valve 21 will build up pressure on the fluid to an increased degree. Unless there is an increase beyond the pressure corresponding to the setting of spring 88, the ball valve 86 will remain closed. This will increase the pressure of the hydraulic fluid in the outlet port 74 and line 20 to thereby move the roll chocks 15 and 16 apart.

Referring again to Figures 10 and 12, it will be appreciated that in the operation of this alternative embodiment of this invention in which the valve there illustrated is used to replace both the main pressure relief valve 21 and the pilot valve 59, that the orifice between chambers 85 and 89 of the valve 70 is seldom fully closed by the pressure control ball 86 and, hence that the lower end 80 of piston 76 is seldom fully seated, with the result that excess hydraulic fluid furnished by the pump 23 is being more or less continuously by-passed back to the oil reservoir 26.

The resistance of the adjustment spn'ng 88 to the passage of this excessive hydraulic fluid is practically continually altered by the action of the drive motor 50 in continually rotating the shaft 58 backward or forward to adjust the position of the screw 91 as required by the change of pressure in the mill stand as measured by the strain gauge on the mill housing 10. In a taper rolling operation, for example, the drive motor more or less continually increases or decreases the pressure of the adjustment spring 88 on the ball 86. It thereby increases or decreases the hydraulic pressure in the main hydraulic fluid conduit 20 and increases or decreases the force applied by the hydraulic jacks 17, 17, 17, 17 to separate the chocks 15 and 16 of the working rolls as the rolling pressure and the strain on the mill stand 10 increases or decreases, giving a substantially constant floating control responsive to the pressure changes on the work rolls. This, in turn, continuously corrects for the deflection of the working rolls 13 and 14 caused by the variations of pressure under which they are working. In this manner unevenness in the rolled sheets, which occurs in ordinary taper rolling operations as described in connection with Figures 1 to 6, is overcome and smooth sheets of even taper are produced. As will be understood from the foregoing description, an important feature of my control 10 system is to utilize the strain on the housing 10 to control the force exerted by the hydraulic jacks 17, 17. While an electrical strain gauge and servo control system of the type described is preferred, a mechanical measurement of the strain and a mechanical-hydraulic system for changing the pressure in the jacks 17, 17 may be used.

The strain measured by the strain gauge is an elongation or contraction of the housing 10 of the rolling mill, within its elastic limits, resulting from the changes in the pressure under which rolls 13 and 14 operate on the sheet being rolled. The extent of this elongation or contraction of the housing is determined by the physical characteristics of the housing itself and by the pressures under which the rolls 13 and 14 are working. The physical characteristics of the housing of any given rolling mill are fixed, and the adjustment of the hydraulic pressure in the jacks 17, 17 can be fixed within any desired range, in terms of the physical characteristics of the housing 10 and the overall range of working pressures of the rolls 13 and 14, by the amplification characteristics of the amplifier 33.

Any given rolling mill will be required to roll sheets which exert substantially diflerent separation pressures on the rolls and, hence substantially different strain on the mill housings. This variation makes desirable an adjustment of the level of the responses of the control system used in accordance with this invention, within ranges determined by the characteristics of the metal being rolled, including the width thereof, and by extent of deformation of the metal required in any pass through the mills. The rheostat 38 provides a convenient means for adjusting the level of the responses of my control system. This rheostat provides a ready means for modifying the level of the voltage supplied by the amplifier 33 to the torque motor 36 to adjust the response range of the synchro system to the range required by the particu lar job being done by the rolling mill.

It will be readily apparent from the foreing description that the method of this invention provides instantaneous and continuous correction for the deflection of the working rolls of a rolling mill and that the method is equally applicable to the rolling of tapered sheets and sheets of uniform thickness. In the control system illustrated, the response of both the electrical system and the hydraulic system to changes in the pressure under which the rolling mill is operating is instantaneous. For this reason, the correction applied to the rolls is completely synchronized with the cause of their deflection. The result is that the difficulties which have heretofore been caused by roll deflection are entirely eliminated.

While preferred embodiments of this invention have been diagrammatically illustrated and described, and various parts of the rolling mill have been omitted for purposes of simplification, it will be understood by persons skilled in the art that various well known controls equivalent to those described and illustrated may be substituted, that multiple control circuits may be used and may be installed on other types of rolling mills than the one specifically illustrated and that various other modifications and changes from the illustrative embodiments shown may be made without departing from the spirit of my invention or the scope of the following claims.

I claim:

1. In a control system for automatically controlling the deflection of the working rolls in a rolling mill comprising a rolling mill stand, two working rolls carried by roll chocks which are free to move relative to the mill stand, and at least two back-up rolls, hydraulic jacks positioned to apply force to separate the chocks of the working rolls and connected through a valve to a source of hydraulic fluid under pressure in excess of the maximum pressure required for separation of the chocks of said working rolls, a strain gauge for registering increases and decreases in the strain on the rolling mill stand during the rolling operation produced by increases and decreases in the pressure under which its rolls are operating, an electrical circuit connected with said strain gauge, a motor and means in said circuit for controlling said motor, means operated by said motor for controlling the operation of the said valve to adjust the pressure on the hydraulic fluid in the said jacks in direct proportion with increases and decreases in the strain on the mill stand as measured by the said strain gauge, and means to adjust the level of response of said electrical circuit.

2. In a control system for automatically controlling the deflection of the working rolls in a rolling mill comprising a rolling mill stand, two Working rolls carried by roll chocks which are free to move relative to the mill stand, and at least two back-up rolls, hydraulic jacks positioned to apply force to separate the chocks of the working rolls and connected through a by-pass valve to a source of hydraulic fluid under pressure in excess of the maximum pressure required for separating the chocks of said working rolls, a strain gauge for registering increases and decreases in the strain on the rolling mill stand during the rolling operation produced by increases and decreases in the pressure under which its rolls are operating, an electrical circuit connected with said strain gauge, a control motor and means in said circuit for controlling said control motor, means operated by said motor for controlling the operation of the said by-pass valve to adjust the pressure on the hydraulic fluid in the said jacks in direct proportion with increases and decreases in the strain on the mill stand as measured by the said strain gauge, a spring loaded torque motor in said electrical circuit which registers as angular deviation the changes in the electrical resistance of the strain gauge, a synchro electrical system to drive said control motor to adjust the said by-pass valve in terms of the angular deviation registered by the said torque motor, and means to adjust the level of response of said electrical circuit.

3. In a control system for automatically controlling the deflection of the working rolls in a rolling mill comprising a rolling mill stand, two working rolls carried by roll chocks which are free to move relative to the mill stand, and at least two back-up rolls, hydraulic jacks positioned to apply force to separate the chocks of the working rolls and connected through a bypass valve to a source of hydraulic fluid under pressure in excess of the maximum pressure required for separating the chocks of said working rolls, a strain gauge for registering increases and decreases in the strain on the rolling mill stand during the rolling operation produced by increases and decreases in the pressure under which its rolls are operating, an electrical circuit connected with said strain gauge, a control motor operated by said circuit, means operated by said control motor for controlling the operation of the said by-pass valve to adjust the pressure on the hydraulic fluid in the said jacks in direct proportion with increases and decreases in the strain on the mill stand as measured by the said strain gauge, a spring loaded torque motor in said electrical circuit which registers as angular deviation the changes in the electrical resistance of the strain gauge, a combination of a synchro generator and a control transformer which generates an electric current when the angular deviation of the said torque motor changes to control said control motor, and means connecting the said control motor to said by-pass valve to adjust the said by-pass valve in terms of the polarity of the said current.

4. In a control system for automatically controlling the deflection of the Working rolls in a rolling mill comprising a rolling mill stand, two working rolls carried by roll chocks which are free to move relative to the mill stand, and at least two back-up rolls, hydraulic jacks positioned to apply force to separate the chocks of the working rolls and connected through a by-pass valve to a source of hydraulic fluid under pressure in excess of the maximum pressure required for separating the chocks of said working rolls, a pilot hydraulic valve connected to and adapted for adjusting the said by-pass valve, a strain gauge for registering increases and decreases in the strain on the rolling mill stand during the rolling operation produced by increases and decreases in the pressure under which its rolls are operating, and an electrical circuit for controlling the operation of said pilot valve from said strain gauge to adjust the pressure on the hydraulic fluid in said jacks in direct proportion with increases and decreases in the strain on the mill stand as measured by said strain gauge, said electrical circuit including a spring loaded torque motor which registers as angular deviation the changes in the electrical resistance of the strain gauge, a combination of a synchro generator and a control transformer which generates an electric current when the angular deviation of the said torque motor changes, a drive motor controlled by said electrical circuit which is operated by the current generated by the control transformer, connections between the drive motor and said pilot valve to adjust the said pilot valve in terms of the polarity and amplitude of the said current, and means to adjust the level of response of said electrical circuit.

5. In a control system for automatically controlling the deflection of the working rolls in a rolling mill comprising a rolling mill stand, two working rolls carried by roll chocks which are free to move relative to the mill stand, and at least two back-up rolls, hydraulic jacks positioned to apply force to separate the chocks of the working rolls and connected through a floating control valve to a source of hydraulic fluid under pressure in excess of the maximum pressure required for separation of the chocks of said working rolls, a strain gauge for registering increases and decreases in the strain on the rolling mill stand during the rolling operation produced by increases and decreases in the pressure under which its rolls are operating, an electrical circuit connected with said strain gauge, a motor and means in said circuit for controlling said motor, means operated by said motor for controlling the operation of the said floating control valve to adjust the pressure on the hydraulic fluid in the said jacks in direct proportion with increases and decreases in the strain on the mill stand as measured by the said strain gauge, and means to adjust the level of response of said electrical circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,323,267 Wittkuhns June 29, 1943 2,339,359 Shayne Jan. 18, 1944 2,345,931 Gates Apr. 4, 1944 2,430,410 Pauls Nov. 4, 1947 2,611,150 Goulding Sept. 23, 1952 2,655,823 Cozzo Oct 20, 1953 2,659,154 Rendel Nov. 17, 1953 2,660,077 Macaulay Nov. 24, 1953 2,680,978 Hessenberg June 15, 1954 2,726,541 Sims Dec. 13, 1955 2,734,407 Smith Feb. 14, 1956 FOREIGN PATENTS 137,260 Sweden Sept. 16, 1952 644,957 Germany Nov. 1, 1934 728,012 Great Britain Apr. 13, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2 9O3 926 September 15 1959 Reymond Mv Reichl It is herebg certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters l atent should read as corrected below.

Column 4, lines, 18 to 21 strike out It may however also be used in rolling of tapered sheets in which strong increases or decreases in pressure occur from end to end of the sheet being rolledfl; column 1O, line 38 for ""foreing read foregoing u,

Signed and sealed this 9th day of August 1960.,

(SEAL) Attest:

KARL Hg AXLIN'E .ROBERT C. WATSON Attesting Officer Commissioner of Patents 

